The long-term goals of this project represent the use of cloned Ia+, IL-1 inducible and Ia+, IL-1 tumor cell clones to determine the molecular events in antigen presentation accessory cell function and the induction of a syngeneic mixed lymphocyte reaction (SMLR). We will continue to use these cell lines as probes to dissect the signals involved in accessory cell function with a particular emphasis on determining the targets of accessory cell function. We will also continue an analysis of antigen presentation of these cell lines with the long-term goal of determining the nature of selective Ia-antigen fragment interaction on the antigen-presenting cell surface. Of particular interest this coming year will be an analysis of the role of the SMLR in the induction of antigen-specific T-cell proliferation. Moreover, our success in establishing a series of T-cell clones and T-cell lines that recognize self-Ia will enable us to approach several other questions concerning the SMLR in a more direct fashion than we had anticipated. In particular we will be asking the following questions: (1)\Is the universe of antigen reactive T cells located with the synreactive population of T cells? (2)\Can synreactive T cells serve as helper cells in a cognitive recognition system with antigen coupled either to purified Ia or to the surface of an Ia+ cell? (3)\Do synreactive T cells provide nonspecific amplification during the induction of what appear to be unrelated immune responses? (4)\Is the T-cell receptor that recognizes self-Ia the same as the antigen-specific T-cell receptor that recognizes antigen in association with Ia? (MI)